Medical imaging using a radiation is performed on a subject matter through a Compton effect that only a portion of energy of a radiation photon is delivered to electrons or a photoelectric effect that all energy is delivered to electrons and a radiation is completely absorbed. At this point, typically a radiation having energy of 10 keV to 200 keV is used.
Digital radiography devices for obtaining a radiographic image are divided into an indirect type equipment and a direct type equipment. In the indirect type equipment, a radiation collides with a scintillator of a scintillator panel to generate a visible light ray, and the visible light ray is transformed to an image signal through a thin film transistor in which a charge coupled device (CCD) or a photodiode is installed. In addition, the direct type equipment obtains an image in a manner that a radiation passing through a subject is directly irradiated on a thin film transistor in which a photoconductor or a photoresistor is installed, and is transformed to an image signal.
In such a radiography system, a radiation radiated from a radiation generating device is irradiated on a wide area at once in a cone type and causes image distortion due to radiation scattering. As a method for removing such a scatter radiation, a method using an anti-scatter grid or an air gap is used.
The grid method uses a difference between a primary radiation almost perpendicularly incident to a radiation detector and a scatter radiation incident in a random direction. This method is to dispose the anti-scatter grid between a subject and a radiation detector, and to physically cut off the scatter radiation, which is obliquely incident in a process where a radiation passing through the subject passes through the grid, from reaching the radiation detector. Here, the anti-scatter grid is composed of lead and aluminum.
The method using the air gap is imaging with a space between a subject and a radiation detector. The scatter radiation is not perpendicularly but obliquely incident to the detector, and when there is the air gap between the detector and the subject, only the primary radiation among photons passing through the subject reaches the radiation detector. On the other hand, the scatter radiation is scattered to the surroundings and does not reach the radiation detector.
However, in a case of adopting the indirect radiation detector using the scintillator panel, although the scatter radiation caused by the subject may be removed using these methods, scattering by the scintillator inside the radiation detector is not removed. In addition, when a radiographic image is obtained by this radiography system, a blurring may occur in the radiographic image, thereby lowering the sharpness of the radiographic image.